While many news reports have focused on the high rates of devastating physical injuries among soldiers returning from Iraq and Afghanistan, a new study, released today, measures another form of casualty: mental illness.

The study, published in the Archives of Internal Medicine, was conducted by Dr. Karen Seal and colleagues at the San Francisco Veterans Affairs Medical Center and the University of California, San Francisco. According to their analysis, about one third of the 103,788 returning veterans seen at V.A. facilities between Sept. 30, 2001 and Sept. 30, 2005 were diagnosed with mental illness or a psycho-social disorder  such as homelessness and marital problems, including domestic violence.

Over half  56%  were suffering from more than one disorder. The median was three disorders, says Dr. Seal: "So instead of treating just post-traumatic stress disorder, you're treating PTSD, depression and substance abuse." The most common combination, she says, was PTSD and depression. "That's understandable," says Seal, because soldiers face horrifying events in combat that lead to PTSD while experiencing "a lot of loss and separation that leads to depression."

Post-traumatic stress disorder affected 13% of veterans in the study. That number is consistent with figures from other conflicts, including Vietnam. But Seal is concerned that the numbers on PTSD and other mental disorders have been rising since the study was completed. "We just did a quick peek at more recent data and the numbers have gone up. They may surpass the numbers from Vietnam." She and her fellow authors attribute the prevalence of mental problems to the stress of guerrilla warfare, the chronic threat of roadside bombs and improvised explosive devices and multiple tours of duty. "A lot of veterans feel they were on the front lines even if they were a cook or a driver," says Seal.

The group with the highest rate of mental problems, according to the study, are those between 18 and 24. Young active-duty soldiers were three times as likely as those over 40 to be diagnosed with PTSD and/or another mental health disorder.

Seal notes that the V.A. has been putting more mental health professionals into primary care facilities, since vets historically have resisted going to mental health clinics. Research suggests that getting them help earlier can prevent PTSD and other problems from becoming chronic.